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CPP: Speed up phi_node > frontier_phi_node > ssa_defn recursion.

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This commit is contained in:
Geoffrey White
2018-10-12 13:19:46 +01:00
parent 6fc5ff53d7
commit a9b55534b4
1 changed files with 7 additions and 1 deletions
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8
cpp/ql/src/semmle/code/cpp/controlflow/SSAUtils.qll
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@@ -124,11 +124,17 @@ cached library class SSAHelper extends int {
* Modern Compiler Implementation by Andrew Appel.
*/
private predicate frontier_phi_node(LocalScopeVariable v, BasicBlock b) {
exists(BasicBlock x | dominanceFrontier(x, b) and ssa_defn(v, _, x, _))
exists(BasicBlock x | dominanceFrontier(x, b) and ssa_defn_rec(v, x))
/* We can also eliminate those nodes where the variable is not live on any incoming edge */
and live_at_start_of_bb(v, b)
}
private predicate ssa_defn_rec(LocalScopeVariable v, BasicBlock b) {
phi_node(v, b)
or
variableUpdate(v, _, b, _)
}
/**
* Holds if `v` is defined, for the purpose of SSA, at `node`, which is at
* position `index` in block `b`. This includes definitions from phi nodes.